Especially due to the rapid technological development in the field of wind power applications, there is currently a high demand for sophisticated converter applications. In particular, power converters, which are able to transfer electric energy from generators with variable frequency and variable output voltage to medium-voltage grids with quasi-constant frequency and voltage in an efficient and reliable way are needed. To achieve these goals, converters with multiple power levels—so-called multi-level converters—can be used.
U.S. Pat. No. 6,301,130 describes a modular multi-level adjustable supply with parallel connected active inputs. This topology is designed to transfer energy from a power network to an electric machine.